Invited speakers

Scientific Motivation

Magnetism is an important, yet incompletely characterized and poorly understood, ingredient of stellar physics.
Magnetic fields are playing a key role in stellar evolution, including accretion processes in young stars, angular
momentum loss, internal mixing. The fields of cool stars govern dynamic, energetic phenomena on stellar surfaces
and significantly influence the stellar environments, including planetary systems. Understanding, e.g., the
cyclic behavior of cool star magnetic fields is critical for assessing possible impact of the solar variability
on our terrestrial climate.

An analysis of the Zeeman effect in spectral lines is the only source of direct information about the strengths
and topologies of stellar magnetic fields. During recent years significant progress has been made by magnetic
broadening and Zeeman-Doppler imaging (ZDI) studies of cool stars. On the one hand, more physically refined and
numerically sophisticated analysis techniques were developed. The number of objects studied with these methods
has increased significantly. This allowed establishing the presence of magnetic fields in essentially all
classes of cool stars and revealing unexpected trends with stellar parameters. Moreover, long-term monitoring
of a handful of sun-like stars yielded first direct observations of magnetic cycles. At the same time, some
puzzling discrepancies between results of the application of different diagnostic methods have been identified,
suggesting that certain aspects of modern observations are not fully understood or even misinterpreted.

This splinter session aims to provide a comprehensive overview of recent results of the direct studies of
magnetic fields at the surfaces of different classes of cool stars. Special emphasis will be given to the
discussion of the reliability and consistency of different magnetic indicators and to the comparison of results
obtained by different research groups.

Proceedings

We are envisioning a single, jointly co-authored review paper including all presenters of the splinter in a
refereed issue of
Astronomische Nachrichten / Astronomical Notes.
Examples of such summary reviews were the stellar magnetism and differential-rotation splinter at CS 17 in
AN 334, 48 and
AN 334, 89.
Every presenter will be asked to contribute a chapter to the paper of length appropriate for the topic.